Pill bug, also spelled pillbug, is a tiny animal that can roll itself into a ball for protection. A pill bug is an invertebrate (animal without a backbone) with seven protective plates on the main part of its back. When a pill bug rolls into a ball, the plates protect its entire body, including the soft underside. Because of pill bugs’ ability to roll into a ball, they may be called roly polies. But other invertebrates that roll into a ball also may be called that.
Pill bugs are not true bugs or even insects. Instead, they are a type of wood louse. They belong to a group of animals called isopods, about half of which live in water. Pill bugs are sometimes called sow bugs. But sow bugs are a different kind of isopod.
Pill bugs are usually gray, brown, or black. They can reach 1/2 inch (13 millimeters) or more in length. Pill bugs have seven pairs of short legs. They have two pairs of antennae, one of which is tiny. They use gills to breathe. Pill bugs require a moist habitat for their gills to work properly. They usually live in spaces in the soil or under rocks or logs. Pill bugs live in many areas of the world.
Pill bugs usually feed on decaying organic matter. This organic matter includes dead plants and animal feces (solid waste). Pill bugs break down this matter and return nutrients to the soil. These nutrients help plants to grow. In this way, pill bugs help to maintain the balance of nature. Pill bugs also sometimes feed on fruit and living plants. They are eaten by such animals as ants, beetles, centipedes, and spiders. They also may be eaten by birds, frogs, lizards, and rodents.
